A can do a work in 9 days while B can do the same work in 18 days, A and B started the work and worked for 4 days then B left the work. In what time A will complete the work? A. 4 Days B. 2 Days C. 3 Days (Your Answer) D. 3.5 Days I M NOT ABLE TO UNDERSTAND HOW THE ANS CAME 3..PLZ EXPLAIN